Everyone knows that exoplanets need to be in the sweet Goldilocks spot (“not too hot, not too cold, just right”) next to their sun to support alien life: but now British boffins have said they reckon oceans might be necessary too.

Researchers at the University of East Anglia, however, have published a new study that shows that the right atmosphere alone may not be enough. Instead of simulating the necessary atmosphere for extraterrestrial life, the boffins looked at the patterns of ocean circulation that a hypothetical Earth-like world would need.

“We know that many planets are completely uninhabitable because they are either too close or too far from their sun. A planet’s habitable zone is based on its distance from the sun and temperatures at which it is possible for the planet to have liquid water,” said David Stevens, from the university's school of mathematics.

“But until now, most habitability models have neglected the impact of oceans on climate. Oceans have an immense capacity to control climate. They are beneficial because they cause the surface temperature to respond very slowly to seasonal changes in solar heating. And they help ensure that temperature swings across a planet are kept to tolerable levels.”

Stevens and his colleagues looked at how different planetary rotation rates would impact heat transport with the presence of oceans.

“We found that heat transported by oceans would have a major impact on the temperature distribution across a planet, and would potentially allow a greater area of a planet to be habitable.

“Mars for example is in the sun’s habitable zone, but it has no oceans – causing air temperatures to swing over a range of 100°C. Oceans help to make a planet’s climate more stable, so factoring them into climate models is vital for knowing whether the planet could develop and sustain life,” he explained.

“This new model will help us to understand what the climates of other planets might be like with more accurate detail than ever before.”

The full study, “The Importance of Planetary Rotation Period for Ocean Heat Transport”, was published in the journal Astrobiology. ®